I don't I am afraid as I am new to Olympus and haven't tried one of the slower lenses but an on-line depth of field calculator will give you an idea. There are many parameters to play with though, including the lens and subject distance.
The comparatively small OMD sensor has the advantage of a larger depth of field for landscape shooters - my picture above of the tower block as pretty much in focus from top to bottom but was taken at f5.6 with the 12mm.
The disadvantage comes for me with head and shoulders portraits, my normal subject. I am looking at a shot of my daughter where her body is half turned to the camera and even with my 75/1.8 the whole of my daughter's face is in focus, as is her leading shoulder and her ear is only just starting to blur. Take this shot with an f2.8 lens and the whole of the head and some of the background is going to get sharp pretty quickly. I am very pleased with the shot but I know that I am not going to be able to get the shots I used to on a full frame with fast protrait lenses where the nose is blurred, eyes are sharp and the rest of the face is blurred. Maybe this isn't a big loss, of course.
If you can manipulate the distance between you, the subject and the background then you can still get a decent degree of subject isolation. But then the next issue is that while a 45mm lens on an OMD has an effective focal length of 90mm, the fall off in focus is slow and gradual because it is still a 45mm lens. Anything some distance from the zone of focus with a fast 90mm lens on a full frame sensor blurs completely because it is a telephoto lens. It doesn't with a 45mm lens on an m34 sensor even of the focal length looks similar because it is a (slight) wide-angle lens. I haven't explained that very well but I hope you get the idea.
m43 isn't a system that makes shallow depth of field shots easy to do and if you might want that look then I would strongly suggest looking at primes or a system with a bigger sensor.